Short answers, pulled from the story.
An island is a piece of land, distinct from a continent, completely surrounded by water. There is no standard size that separates islands from continents, and islands can occur in lakes, rivers, and seas. Low-tide elevations, which are not above the surface at high tide, are generally not considered islands.
Oceanic islands form through volcanic activity, often above hotspots where the mantle is hotter than the surrounding rock. They can also grow into atolls from coral reefs around a central lagoon, or form as barrier islands from sediment deposited by waves along shorelines.
The island rule, also called Foster's rule, states that small mammals such as rodents tend to evolve larger on islands, a trend called island gigantism, while larger animals such as the hippopotamus tend to become smaller, called insular dwarfism. The giant tortoise of the Seychelles and the pygmy hippopotamus are examples.
Darwin's finches, up to fifteen tanager species endemic to the Galapagos Islands, evolved different beaks to eat different foods, an example of adaptive radiation. Charles Darwin observed these and other species when he reached the Galapagos in 1835 aboard HMS Beagle, which helped him formulate the theory of natural selection.
Low-lying island nations such as Maldives, the Marshall Islands, and Tuvalu are threatened with complete submersion by sea level rise. The Marshall Islands is a country of 1,156 islands, and Tuvalu signed an agreement allowing 280 of its citizens to become permanent residents of Australia each year.
The Polynesians were the first to colonize distant oceanic islands, traveling as far as 2000 to 3200 kilometers to reach places such as Tahiti. Between 1100 and 800 BC they sailed east from New Guinea and the Solomon Islands to reach modern-day Fiji and Samoa, eventually settling Easter Island and New Zealand.
Artificial islands are made by humans through land reclamation, using methods such as revetments or permanent caissons filled with sand or gravel. The first permanent artificial island is Al-Sayah in Bahrain, created at least 1,200 years ago, while modern examples include Pearl Island in Qatar and the Palm Islands in Dubai.